The family of a grandmother murdered by a woman who was released into the community despite having killed her mother have questioned why she had been set free.

Nicola Edgington killed Sally Hodkin in an attack in the street in 2011, two years after she had been released into community care from an unlimited sentence in a psychiatric institution for manslaughter.

During the trial a psychiatrist said that Edgington had been misdiagnosed with schizophrenia at her first trial in 2005.

Mrs Hodkin's family said after Edgington was found guilty of her murder at the Old Bailey on Thursday that she should not have been free.

In a statement, the family said: "This cannot have been the right decision, otherwise we would not be here today.

"We cannot quite understand how or why Nicola Edgington was released back into society so soon after killing her own mother.

"The savage attack on Sally Hodkin by Nicola Edgington was not a normal stabbing. She continued to attack Sally whilst she was on the floor. She slit her throat with a meat cleaver and nearly decapitated her.

"It is our opinion that this woman should never be released back into society. The public need to be protected from people like her."

The five-week trial heard that Edgington had already attacked another woman, Kerry Clark, at a bus stop in Bexleyheath, south east London, on October 10, 2011.

Miss Clark, 24, managed to fight off Edgington, who then went looking for another victim.

Sally Hodkin, 59, was walking to work along a busy shopping street when she was attacked.

Edgington attacked her with a knife, killing her.

The 31-year-old had only been released from the Bracton Centre in 2009, where she was being held after being given an indefinite sentence for manslaughter.

The Bracton Centre medium secure unit is run by the Oxleas NHS Foundation Trust, which is also responsible for Oxleas House.

She was being treated at a mental health unit in 2011 at the time of the murder, but was able to walk out unopposed.

In 2006, she had been found guilty of killing her mother in a knife attack a year earlier.

Before that trial, Edgington was diagnosed with schizophrenia and pleaded guilty to manslaughter on the grounds of diminished responsibility.

She was ordered to be detained under the Mental Health Act without limit of time.

During her second trial, forensic psychiatrist Dr Philip Joseph said Edgington had been misdiagnosed on the evidence available at her first trial.

He said her actions had been deliberate and not those of someone who was so ill they did not know what they were doing.

A Ministry of Justice spokesman said: "The decision to discharge Nicola Edgington in 2009 was made by officials, without reference to ministers, under authority which is delegated as a matter of routine by the Secretary of State."

The health authority in charge of Nicola Edgington's care promised a "full and thorough" inquiry into the events which led up to the murder.

Chief executive of Oxleas NHS Foundation Trust Stephen Firn said it was "a matter of extreme regret" that she was able to leave a mental health unit on the day of the stabbings, but a report into her treatment found that the decision to let her live in the community in 2009 was sound.